Check model existence before unloading

Add a check to ensure model exists before unloading.

subgen.py

@@ -1,4 +1,4 @@
-subgen_version = '2026.01.3'
+subgen_version = '2026.01.4'
 
 """
 ENVIRONMENT VARIABLES DOCUMENTATION
@@ -797,9 +797,10 @@ def delete_model():
     global model
     if clear_vram_on_complete and task_queue.is_idle():
         logging.debug("Queue idle; clearing model from memory.")
-        model.model.unload_model()
-        del model
-        model = None
+        if model:
+            model.model.unload_model()
+            del model
+            model = None
         if transcribe_device.lower() == 'cuda' and torch.cuda.is_available():
             torch.cuda.empty_cache()
             logging.debug("CUDA cache cleared.")